JP3315944B2 - Water treatment method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a boiler,
Air conditioning equipment, refrigeration equipment, water treatment method for equipment using water represented by papermaking equipment, more specifically, to prevent the generation of scale in boilers, air conditioning equipment, refrigeration equipment, papermaking equipment It relates to a method for treating water.

[0002]

2. Description of the Related Art Conventionally, for example, water for equipment using water, such as the boiler, air conditioning equipment, refrigeration equipment, and papermaking equipment described above, when its hardness is high, passes through an ion exchange tower or precipitates. 2. Description of the Related Art A pretreatment such as filtration after adding an agent such as an agent is performed to remove a hardness component in the water.

[0003]

In the above-mentioned conventional water treatment, for example, when the above-mentioned water is treated and supplied through an ion exchange tower, silica in the water is difficult to remove, and the remaining dissolved solid matter is hardly removed. Is not easy to remove. In particular, when used in refrigeration equipment, it is difficult to prevent precipitation of silica, whose solubility is extremely reduced at low temperatures. Further, in the case where the feed water temperature of a boiler or the like increases, the concentration of dissolved solids is inevitable due to the circulating use of the water, and in order to prevent the adhesion of scales to the circulating water channel wall, an inhibitor or the like It is necessary to repeatedly add the drug to the water during circulation use. Further, if the water is subjected to the ion exchange treatment during circulation, there is a problem that much trouble is required for the treatment of the water, such as an increase in the number of times the ion exchanger is washed in order to extremely increase the load on the ion exchange tower. are doing. Further, in the refrigeration equipment, even if a small amount of silica remains in the feed water, its solubility decreases with cooling and the silica precipitates, thereby forming nuclei that induce freezing of the water, Has a problem that it is difficult to increase the refrigeration efficiency because the supercooling is inhibited.

[0004] Therefore, a method for treating water according to the present invention comprises:
In view of the above-mentioned problems, it is an object of the present invention to provide a means for easily removing solids mainly containing dissolved silica by adding a small amount of a chemical without increasing the size of the apparatus.

[0005]

[Characterizing feature of the present invention] SUMMARY OF THE INVENTION The first characteristic feature of the processing method of the water of the present invention relating to Claim 1, adding an amphoteric metal hydroxyl salts in water supplies or
After the formation of the amphoteric metal hydroxyl salt , the water is cooled below the freezing point to freeze the ice, the precipitate in the frozen ice is separated, and the silica in the water is removed.

A second feature of the method for treating water according to the present invention according to claim 2 is that, in order to separate the sediment in the first feature, the frozen ice is separated from the cooled water. .

According to a third aspect of the method for treating water according to the present invention, in order to separate the sediment in the first aspect, all the frozen ice is melted and then cooled. The point is to separate the precipitate by filtering the water.

[0008] The fourth characteristic configuration of the processing method of the water of the present invention relating to claim 4, metal hydroxyl salts to be added in the second feature structure or the third characteristic feature is that an aluminum hydroxyl salts.

A fifth aspect of the method for treating water according to the present invention according to the fifth aspect is the above-mentioned fourth aspect, wherein the hydroxyl group salt of aluminum is soluble in the water for use in an amount equivalent to 0.1 in terms of aluminum. lies in Ru dissolved or 3 ppm.

[0010] The sixth characteristic configuration of the processing method of the water of the present invention according to claim 6, serial metal hydroxyl salts to be added in the second feature structure or the third characteristic feature is the zinc hydroxyl salt <br/> On the point.

A seventh aspect of the method for treating water according to the present invention according to claim 7 is that, in the sixth aspect, the hydroxyl group salt of zinc is soluble in the water for use in an amount equivalent to 0.1 as zinc.
Lies in Ru dissolved least 5 ppm.

According to the first feature of the method for treating water according to the present invention, dissolved silica can be easily separated by adding a small amount of a chemical and cooling. In other words, the amphoteric metal hydroxide salt has a strong affinity for silica when precipitated, and easily becomes a crystal nucleus of silica.Furthermore, since the solubility is extremely low at low temperatures, fine crystals can be easily precipitated by cooling to near the freezing point. I do. Therefore, the amphoteric metal hydroxyl salt is added.
Alternatively, by producing and cooling, silica in the water for use can be easily precipitated as crystals. Since the precipitation of the silica induces freezing of the service water, the separation of the silica from the service water is easy, and it is easy to supply the service water having an extremely low silica content. This is because dissolved silica in service water is a conjugate of various forms, and its composition cannot be specified, and therefore its solubility limit cannot be determined, but groundwater containing a large amount of silica, Upon cooling to below freezing, it was found that silica was present in the frozen ice. The phenomenon that silica is present in this ice is
It is remarkable when you are dissolved as SiO ₂ 40 ppm or more in the water. Generally, 10p as SiO ₂
At a dissolved amount of about pm, silica content in ice is often not detected, but when both amphoteric metal hydroxide salts such as aluminum or zinc hydroxide salts are dissolved in the above-mentioned water, the silica content is not detected. The present inventors have found that the above-mentioned silica content is present in the above-mentioned. The first characteristic configuration is based on this new finding. The above-mentioned amphoteric metal hydroxide salt is in a dissociation equilibrium state with the cation of the metal (such as the cation of aluminum or the cation of zinc) and dissolves the cation of the metal, but when cooled to around the freezing point, The solubility of the metal hydroxide salt is extremely reduced. As a result, the metal hydroxide salt dissolved in the service water becomes supersaturated, and its precipitation occurs to generate fine crystals of the metal hydroxide. Since the affinity between the precipitated amphoteric metal hydroxide and the dissolved silica component is good, the precipitation of the dissolved silica component is induced using the fine crystals of the metal hydroxide as nuclei. With the precipitated crystals of the silica as nuclei, supercooled water freezes. Therefore, even with a relatively low concentration of dissolved silica, silica coexists in the ice due to the coexistence with the amphoteric metal hydroxide salt.

The second aspect of the method for treating water according to the present invention is as follows.
According to the characteristic configuration, the sediment taken into the ice is separated from the ice, so that the separation from the service water is further facilitated while exhibiting the operational effects of the first characteristic configuration. In other words, the crystals of the metal hydroxide salt induce crystallization of silica,
Since the precipitated silica crystals become the core of ice formation, the precipitate will be taken into the ice, and if the ice is separated, the core silica crystals will be separated at the same time. is there. If you cool the water to near freezing,
Since the ice easily floats and the ice floats, almost all of the precipitated silica can be easily separated from the water.

The third aspect of the method for treating water according to the present invention is as follows.
According to the characteristic configuration, while the operation and effect of the first characteristic configuration are exhibited, the precipitate is taken in the ice and separated after the ice is melted, so that the precipitate can be surely separated. That is, when the water freezes, solids are taken in as crystal nuclei. If a precipitate precipitates, it is taken in as a crystal nucleus. Therefore, when the ice is melted, the precipitate in the ice can be easily separated from water by filtration.

The fourth aspect of the method for treating water according to the present invention is as follows.
According to the feature configuration, the operation and effect of the second feature configuration or the third feature configuration are further made effective. That is, the hydroxyl group of aluminum dissociates to produce aluminum cations. The aluminum cation is in equilibrium with the aluminum hydroxide, and the solubility of the aluminum hydroxide becomes extremely low as the temperature decreases. Therefore, the aluminum cation can be sequentially precipitated as an aluminum hydroxide in a supercooled state. Due to the high affinity between the fine crystals of this aluminum hydroxide and silica, it is easy to become precipitation nuclei of silica crystals,
Even a low concentration of dissolved silica can be precipitated. This is more effective if it is precipitated in a supercooled state.

The fifth aspect of the method for treating water according to the present invention.
According to the characteristic configuration, the amount of drug added can be extremely reduced while exhibiting the operation and effect of the fourth characteristic configuration. That is, since it is of Ru was originally dissolved within less aluminum soluble hydroxyl salt water of solubility, hydroxyl salts of said aluminum is the need in small amounts. Since the aluminum hydroxide precipitated by cooling the water for use is a fine crystal, a sufficient number of crystals are generated even in a small amount. Therefore, it becomes possible to precipitate silica using these fine crystals as nuclei. If the amount of the aluminum hydroxide salt exceeds the range soluble in water, precipitation occurs from the time of drug addition,
Because it becomes difficult to form a supercooled state when cooling the water,
It becomes difficult to precipitate fine crystals that should serve as nuclei for silica crystal precipitation. Further, if the amount of the aluminum hydroxide salt is less than 0.3 ppm in terms of aluminum, the ratio of the soluble component of the aluminum hydroxide becomes too high, and the ratio of precipitation with cooling becomes low. The effect of the addition may be impaired. Therefore, even if the amount of the aluminum hydroxide salt to the service water is excessive or insufficient,
The effect may be diminished.

The sixth aspect of the method for treating water according to the present invention.
According to the feature configuration, the operation and effect of the second feature configuration or the third feature configuration are further made effective. That is, the hydroxyl group of zinc dissociates to generate zinc cations. The zinc cation is in equilibrium with the zinc hydroxide, and if the temperature is lowered, the solubility of the zinc hydroxide becomes extremely low. Therefore, the zinc cation can be sequentially precipitated as a zinc hydroxide in a supercooled state. Due to the high affinity between the fine crystals of the zinc hydroxide and the silica, the zinc hydroxide is likely to become a precipitation nucleus of the silica crystals, and even a low concentration of dissolved silica can be precipitated. This is more effective if it is precipitated in a supercooled state.

The seventh aspect of the method for treating water according to the present invention.
According to the feature configuration, the amount of drug added can be extremely reduced while exhibiting the operation and effect of the sixth feature configuration. In other words, within the range of solubility of zinc hydroxide, which originally has low solubility, in water
Since it is of Ru dissolved, hydroxyl salts of said zinc is the need in small amounts. Since the zinc hydroxide precipitated by cooling the service water is a fine crystal, a sufficient number of crystals are generated even in a small amount. Therefore, it becomes possible to precipitate silica using these fine crystals as nuclei. In addition, when the amount of the hydroxyl salt of zinc exceeds the range of solubility in service water, since precipitation occurs from the time of adding the drug , it becomes difficult to form a supercooled state when cooling the service water, and it becomes a core of silica crystal precipitation. There is a possibility that it becomes difficult to precipitate fine crystals to be formed. Further, if less than 0.5ppm by volume zinc equivalent amount of hydroxyl salts of said zinc, too high ratio of solubles zinc hydroxide, the ratio is lowered to precipitate with the cooling, the The effect may be impaired. Therefore, even if the amount of the hydroxyl group salt of zinc in the water for use is excessive or insufficient, the effect may be reduced.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of a method for treating water according to the present invention will be described below. The method of treating water described below is performed by cooling the water to a temperature below freezing in a water supply path for supplying water to equipment using water typified by boilers, air conditioning equipment, refrigeration equipment, and papermaking equipment. Related to the treatment of water for precipitating and removing dissolved solids mainly containing silica dissolved therein, prior to cooling in the supply path, in a temperature range above the freezing point, such as aluminum or zinc in the water for use. Addition of amphoteric metal hydroxide salt or formation of metal hydroxide salt
Is shall not. After that, by cooling to below freezing point,
The dissolved solid is deposited, and the deposited solid is separated and removed.

[First Embodiment] In order to separate and remove the precipitated solid, water is cooled to a temperature below the freezing point to remove frozen ice and supply water.
That is, an amphoteric metal hydroxyl salt such as aluminum or zinc is added to a water containing a dissolved solid mainly composed of silica at a temperature higher than the freezing point. The addition amount of the aluminum hydroxide salt is below the limit of solubility in water at the temperature at which it is added, and is 0.3 ppm or more in terms of aluminum. The addition amount of the zinc hydroxide salt is below the limit of solubility in water at the addition temperature, and is 0.5 pp in terms of zinc.
m or more. In any case, if it is added beyond its solubility limit, a precipitate is formed at the time of addition, which causes precipitation of silica immediately near the freezing point, and then shifts to a supercooled state. Since the amount of dissolved solids deposited is reduced, it is preferable that the amount of addition be smaller than this. Further, if the addition amount is less than the lower limit, the ratio of the dissolved amount after cooling is high, and it is difficult to be in a supercooled state, so the amount of precipitation of fine crystals of the metal hydroxide is reduced, Since there is a possibility that the number of crystal nuclei of the silica component may be insufficient, the amount is preferably not less than the lower limit. After adding the amphoteric metal hydroxide salt such as aluminum or zinc, the water is cooled to below freezing. The rate of freezing the water may be, for example, half of the water,
In addition, it may be one-third of the amount of water for use, and is appropriately determined depending on the dissolved amount of the solid, the composition and properties of the silica component.

With the cooling of the service water, the metal hydroxide first becomes supersaturated and becomes supercooled. As a result, the dissolved state of the metal hydroxide becomes unstable, and fine crystals precipitate. The precipitation of the fine crystals induces the precipitation of a supercooled silica component having a good affinity for the fine crystals. When the silica component is precipitated, the water is frozen with the crystals as nuclei. Therefore, if this ice is separated, service water with a low dissolved solid content can be taken out. In the frozen state, only the lower water may be taken out for water supply, and if the ice is fine, it may be filtered by a screen or a filter. According to the above method, originally amphoteric metal hydroxyl salt having low solubility in water,
Since it is dissolved in the working water, the amount of addition of the amphoteric metal hydroxyl salt is small, and after that, it is only cooled and only ice is separated. Also does not require large ones. As the cold heat source, it is easy to use waste cold heat.

[Second Embodiment] To separate and separate the precipitated solid, the water is cooled to a temperature below the freezing point to freeze the ice, and then the temperature is raised to melt the frozen ice again to melt the ice. After that, the water is filtered and supplied. That is, an amphoteric metal hydroxyl salt such as aluminum or zinc is added to a water containing a dissolved solid mainly composed of silica at a temperature higher than the freezing point. The addition amount of the aluminum hydroxide salt is below the limit of solubility in water at the temperature at which it is added, and is 0.3 ppm or more in terms of aluminum. The amount of the zinc salt of zinc to be added is not more than the limit of solubility in service water at the temperature at which the zinc is added.
ppm or more. In any case, if it is added beyond its solubility limit, a precipitate is formed at the time of addition, which causes precipitation of silica immediately near the freezing point, and then shifts to a supercooled state. Since the amount of dissolved solids deposited is reduced, it is preferable that the amount of addition be smaller than this. In particular, aluminum hydroxide and zinc hydroxide are
If both are added to service water in excess of 10 ppm in terms of aluminum and zinc, respectively, aluminum hydroxide or zinc hydroxide precipitates in the service water as oozeous sediment, and it becomes difficult to separate them. The upper limit of the addition of both oxide and zinc hydroxide is 10 ppm in terms of aluminum and zinc, respectively. Further, if the addition amount is less than the lower limit, the ratio of the dissolved amount after cooling is high, and it is difficult to be in a supercooled state, so the amount of precipitation of fine crystals of the metal hydroxide is reduced, Since there is a possibility that the number of crystal nuclei of the silica component may be insufficient, the amount is preferably not less than the lower limit. After adding the amphoteric metal hydroxide salt such as aluminum or zinc, the water is cooled to below freezing point. After the ice is appropriately frozen, the temperature is raised again to melt the ice, and the filtered water is supplied. The rate of freezing the water, for example, may be the entire amount of the water, may be half the amount, or may be one third of the amount of the water, the dissolved amount of solids, silica It is determined appropriately according to the composition and properties of the minute.
If the whole amount of the service water is frozen, there is a possibility that most of the dissolved solids can be removed.

With the cooling of the water, the amphoteric metal hydroxide first becomes supersaturated and becomes supercooled. as a result,
The dissolved state of the metal hydroxide becomes unstable, and fine crystals precipitate. The precipitation of the fine crystals induces the precipitation of a supercooled silica component having a good affinity for the fine crystals. When the silica component is precipitated, the water is frozen with the crystals as nuclei. Therefore, when this ice is melted, dissolved solids mainly composed of silica taken in the ice precipitate. If the precipitated solid is filtered off with a filter, service water with a low dissolved solid content can be obtained. According to the above method, originally amphoteric metal hydroxyl salt having low solubility in water,
Since it is dissolved in the water, the amount of the metal hydroxyl salt added is small, and after that, it is only cooled and returned to normal temperature,
The operation is simple, the amount of drug added is small, and large equipment is not required. As the cold heat source, it is easy to use waste cold heat.

[0024]

(First embodiment)

As a comparative example, test water from which raw water was brought into contact with a sodium-based cation exchanger to remove aluminum and zinc cations as a test water was prepared as a comparative example. For this example, zinc hydroxide was converted to zinc per 1 liter of test water. Test water to which 1.2 mg was added in reduced amount was prepared. Each of these test waters was weighed exactly 1 liter, filled in a 1 liter polypropylene beaker, placed in a freezer maintained at -10 ° C, and stored frozen in the respective refrigerators. When half of the ice had frozen, the beaker was taken out of the freezer, water and ice were separated, and the water and ice were returned to room temperature, respectively, and the solid content was filtered with a filter having a maximum transmission diameter of 1 micron. After filtration, each filtered water was subjected to analysis. The analysis results are as shown in Table 1.

[0025]

[Table 1]

As shown in Table 1, in the comparative example, no solids were detected in the raw water, the ice portion, and the water portion, and only in the examples, solids were detected in the ice portion. At the same time, as for silica, the ice part and the water part are almost uniformly detected in the comparative example, whereas in the example, the detection amount in the ice part is reduced, and the total amount is reduced. In the embodiment, after the freezing treatment, the zinc component is not detected in both the ice portion and the water portion. The test results in this example indicate that the freezing treatment caused the zinc component to precipitate out, possibly as a zinc hydroxyl group salt, along with which the silica crystallized out and was frozen using this as a nucleus. In order to confirm this point, the solid separated in the example was subjected to X-ray analysis.
%, 19% zinc and 7% calcium. Therefore, it was proved that the dissolution of the hydroxyl group salt of zinc accelerated the precipitation of dissolved solids such as silica and calcium, and induced icing by using these as nuclei. Although not shown as an example, similar experiments have revealed the same facts in the case of aluminum hydroxide.

Second Embodiment Raw water from which aluminum and zinc cations have been removed by contact with a sodium-based cation exchanger is prepared, and zinc chloride and sodium carbonate are formed in the raw water to produce zinc hydroxide. at an equivalent ratio, as zinc, 0.5ppm, 1.0pp
m, an amount corresponding to 3.0 ppm was added, and test water for an example relating to a hydroxyl group of zinc was prepared.
Polyaluminum chloride, in an equivalent ratio to produce aluminum hydroxide, as A aluminum, 0.3 ppm,
0.5 ppm, adding an amount corresponding to 2.0 ppm,
Example test water for a hydroxyl salt of aluminum was prepared. The raw water was used as it was as a test water for a comparative example. Each test water was accurately weighed in 1 liter, filled in a 1 liter polypropylene beaker, placed in a freezer maintained at -10 ° C, and stored frozen in the respective refrigerators. After the whole amount was frozen, the beakers were taken out of the freezer, each was returned to room temperature, and the solid content was filtered through a filter having a maximum transmission diameter of 1 micron, and each filtered water was subjected to analysis. The analysis results are as shown in Table 2.

[0028]

[Table 2] Note and fruit-1: Zinc is added together with sodium carbonate in the form of zinc chloride.
Addition. The addition amount was 0.5 pp as zinc in terms of zinc hydroxide production equivalent ratio.
m. Fruit-2: Zinc is added together with sodium carbonate in the form of zinc chloride. The addition amount is 1.0 pp as zinc in terms of zinc hydroxide production equivalent ratio.
m. Fruit-3: Zinc is added together with sodium carbonate in the form of zinc chloride. The addition amount was 3.0 pp as zinc in terms of zinc hydroxide production equivalent ratio.
m. Real-4: Add aluminum in the form of polyaluminum chloride
Addition. The addition amount is 0.3 ppm as aluminum. Real-5: Add aluminum in the form of polyaluminum chloride
Addition. The addition amount is 0.5 ppm as aluminum. Real-6: Add aluminum in the form of polyaluminum chloride
Addition. The addition amount is 2.0 ppm as aluminum.

As shown in Table 2, a zinc hydroxide salt or an aluminum hydroxide salt is formed and added in water.
By adding the zinc compound or aluminum compound and the hydroxyl group-providing compound, solids are formed in the frozen ice, and the amount of dissolved silica in the water after the treatment is reduced. At least, if it is a zinc hydroxyl salt, it is 1.0 ppm or more in terms of zinc, if it is an aluminum hydroxyl salt,
It was found that the amount of dissolved silica can be reduced by half by adding 0.5 ppm or more in terms of aluminum.

The results of the above Examples show that the addition of zinc hydroxide or aluminum hydroxide which is an amphoteric metal hydroxide precipitates a dissolved solid mainly composed of silica upon cooling. . Therefore, it is possible to remove the silica content in the service water, and supply the water to be supplied to equipment using water, such as a boiler, an air conditioner, a refrigeration facility, and a papermaking facility, to the silica in the flow channel of these facilities. It is clear that the silica content can not be contained before the formation of a scale mainly composed of silica.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI B01D 9/02 608 B01D 9/02 608A 615 615Z 617 617 C02F 1/44 C02F 1/44 E 5/00 610 5/00 610F 620 620C 5/02 5/02 B (72) Inventor Machiko Ogawa 2-1-161 Shiromi, Chuo-ku, Osaka City, Osaka Prefecture Inside Tozai Chemical Industry Co., Ltd. (72) Inventor Ikuo Sakai 2-chome, Araimachi, Takarai City, Hyogo Prefecture 1-1 1-1 Mitsubishi Heavy Industries, Ltd. Takasago Works (72) Inventor Seiichi Tsuji 2-1-1, Araimachi, Araimachi, Takasago-shi, Hyogo Prefecture Mitsubishi Heavy Industries, Ltd. Takasago Works (72) Inventor Sumio Yamauchi Araimachi, Takasago-shi, Hyogo Prefecture 2-1-1 Niihama Mitsubishi Heavy Industries, Ltd. Takasago Research Laboratory (56) References JP-A-4-260494 (JP, A) Open flat 7-185527 (JP, A) (58 ) investigated the field (Int.Cl. ^7, DB name) C02F 1/22 B01D 9/02 C02F 5/00

Claims (7)

(57) [Claims] 1. A method for treating water for equipment using water, comprising adding an amphoteric metal hydroxide salt to said water or adding an amphoteric metal to the water.
A method for treating water for cooling the water to a temperature below the freezing point to freeze the ice after generating a hydroxyl salt, separating a precipitate in the iced ice, and removing silica in the water. 2. The method of claim 1, wherein the frozen ice is separated from the cooled water to separate the precipitate. 3. The method for treating water according to claim 1, wherein the precipitate is separated by melting all of the frozen ice and then filtering the cooled water to separate the precipitate. Wherein said metal hydroxyl salts, the processing method of the water according to claim 2 or 3 which is an aluminum hydroxyl salts. 5. The method according to claim 1, wherein the aluminum hydroxide salt is
, In the range of soluble, 0.3P of aluminum equivalent amount
processing method of water according to claim 4, wherein Ru is dissolved or pm. 6. The metal hydroxide salt is a zinc hydroxide salt .
The method for treating water according to claim 2 or 3. 7. The method of treating water for use according to claim 6, wherein the hydroxyl group salt of zinc is dissolved in the water for use in an amount of 0.5 ppm or more in terms of zinc within a range of solubility .